What Direction For Planting Bulbs – How To Tell Which Way Is Up On A Flower Bulb


By: Susan Patterson, Master Gardener

While it may seem simple and straightforward to some people, which way to plant bulbs can be a bit confusing to others. It’s not always that easy to tell which way is up when it comes to what direction for planting bulbs is best, so read on to learn more.

What is a Bulb?

A bulb is typically a sphere-shaped bud. All around the bud is a fleshy membrane called scales. These scales contain all the food the bulb and flower will need to grow. There is a protective coating around the bulb called a tunic. There are different types of bulbs with a few differences, but the one thing they all have in common is they produce a plant from an underground food storage supply. They all perform better when planted correctly.

Bulbs and corms are very similar to each other. The only real difference is the way they store food, and corms are much smaller and tend to be flatter in shape rather than round. Tubers and roots are similar to each other in that they are just enlarged stem tissue. They come in all shapes and sizes, from flat to oblong and sometimes come in clusters.

Planting Flower Bulbs – Which Way Up

So, which way up do you plant bulbs? Bulbs can be confusing when trying to figure out the top from the bottom. Most bulbs, not all, have a tip, which is the end that goes up. How to tell which way is up is by looking at the bulb and locating a smooth tip and a rough underside. The roughness comes from the roots of the bulb. Once you have identified the roots, face it downward with the pointy tip up. That is one way to tell which way to plant bulbs.

Dahlia and begonias are grown from tubers or corms, which are flatter than other bulbs. Sometimes it is tricky to determine what direction for planting bulbs in the ground because these don’t have an obvious growing point. You can plant the tuber on its side and it will normally find its way out of the ground. Most corms can be planted with the concave portion (dip) facing upwards.

Most bulbs, however, if planted in the wrong direction, will still manage to find their way out of the soil and grow toward the sun.

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Read more about General Bulb Care


How to Plant the Pointy Part of a Gladiolus Bulb

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Gladiolus (Gladiolus spp.) bulbs earn their "glad" nicknames by sending up tall spires of blooms every year. Glads are available in a range of bloom colors, including purple, red, orange and pastel shades. Although glads are known as back-of-border all-stars, some reaching as much as 6 feet tall, dwarf varieties also are available. Glads are hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 7 to 10, which means in those locations their bulbs don't have to be dug up every fall for indoor storage until spring. Gardeners in all locations, however, should plant the onion-shaped bulbs properly, which leads to the classic question, "Which end is up?"

Enrich a sunny planting area with a 3-inch layer of compost worked into the top 4 to 6 inches of soil. Planting gladiolus bulbs can begin in spring as soon as the danger of frost is gone.

Dig a hole about 4 1/2 inches deep and 24 inches in diameter.

Scatter one handful of 5-10-5 fertilizer, or equal parts bonemeal and compost, into the bottom of the hole.

Place 1/4 to 1/2 inch of soil, which you removed to make the hole, over the fertilizer. The soil layer prevents gladiolus bulbs from having direct contact with the fertilizer.

Place one gladiolus bulb, with its flatter, larger side facing downward, about 6 inches from the hole's side. The bulb's pointed, narrow end should face upward.

Set three or four more bulbs in the hole, placing them about 6 inches from each other and the hole's side. Ensure all the bulbs have their pointed-side facing upward.

Cover the bulbs with the soil you've removed to make the hole, adding additional topsoil if necessary. Firm the soil lightly.

Water the garden bed thoroughly.

Repeat the planting procedure, if desired, every two weeks in other garden beds or in sections of the same garden bed. This optional task will result in continuous glad blooms if you plant glad bulbs from spring to midsummer.

  • About 4 inches is the average depth at which gladiolus bulbs should be planted, but examine the bulbs before planting them in order to ensure the best planting depth. The smallest bulbs should be planted 2 inches deep while large bulbs do best at 6 inches deep.
  • Although northern gardeners dig up gladiolus bulbs in fall, glad bulbs planted outdoors in USDA zones 7 through 10 will survive if left in the ground year after year. The general belief, however, is that removing glad bulbs in all locations in fall for spring replanting causes the plants to bloom best, according to the Missouri Botanical Garden website.
  • Stake tall gladiolus varieties to keep them from toppling during heavy wind and rainfall.
  • Glads resent overwatering. Weekly watering is necessary only during dry spells. Overly moist soil results in fungal diseases, to which gladiolus flowers are susceptible.

Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.


8 summer bulbs to consider planting now

How do I plant summer bulbs?

According to Tom, it's very straightforward. You're simply planting bulbs into the ground, but here’s a step-by-step guide from the gardener, for your reference.

  1. Plant the bulb with its tip pointing upwards and roots pointing down. This may seem obvious, but it’s not always easy to tell which end of a bulb is which. If you can’t tell the tip from the roots, plant the bulb on its side and it will find its own way.
  2. A rule of thumb with planting bulbs is to plant them twice the depth of the bulb.
  3. Most bulbs prefer a well-drained fertile soil but always add a handful of grit to the hole before dropping in the bulb. If your soil is very wet and heavy, consider planting bulbs in pots rather than in the ground.
  4. Fill in the hole and compact gently.

Remember this: as a general rule of thumb, plant summer bulbs about three times their depth into a mix of sharp sand and good peat-free compost. Decent drainage is key.

Top tips from Mark: If you want to get a head start on summer you can grow summer bulbs indoors in a greenhouse, conservatory or warm porch a month or two before transplanting outdoors.

"If you do this with dahlias, you can take basal cuttings during the spring from the new growth and increase your stock for free - but please always check for plant breeder’s rights," he shares.

When do summer bulbs flower?

It'll depend from bulb to bulb, but largely, they'll flower across the summer months, which gives you plenty to look forward too.

What care do summer bulbs need?

Again, it'll vary from flower to flower, so always read the packet as it'll give you clear instruction on how to plant and care for your bulb.

Mark and Tom both advise watering regularly, as you would do for any other flowering plant, but being mindful not to overwater and drown the bulbs. As above, they're prone to rotting, and it's a fine line.

Once your bulbs are blooming, aim to water around three times a week.

Which summer bulbs do best in pots?

Not got much space but still keen to get planting?

Funnily enough, summer bulbs actually do best when planted in pots, so you're in luck. "All of the summer bulbs mentioned above are perfect for growing in pots and containers," shares Mark.

He goes on to add that agapanthus, in particular, flowers best when its roots are constricted. "Agapanthus grow on rocky outcrops in South Africa, so by adding horticultural grit or sand into peat-free multi-purpose compost, it will help with drainage, just like the rocks and natural environment from its native origin."

Not sure how to plant in a pot? Let Tom's tips help.

  1. Choose pots with good drainage holes.
  2. Place a few crocks (pieces of broken pottery) in the bottom of the pot to stop drainage holes clogging up with compost.
  3. Raise pots on pot feet in winter to improve drainage

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Tender Bulbs

Bulbs are little wrinkled miracles -- both underground storehouses and flower factories. The small package contains all that the plant needs to grow and flower. While hardy bulbs require a cold period to thrive, tender bulbs that flower in the summer cannot survive winter in the ground. Included in this category are such summer favorites as dahlias (Dahlia spp.) and begonias (Tuberosa spp.) that make a summer garden vivid with color and rich with texture. They thrive in U.S. Department of Agriculture plant hardiness zones 7 though 10 and 9 though 11 respectively. If you follow simple guidelines for digging up and storing tender bulbs, they provide summer pleasure for many years.


Planting depths for bulbs and tubers

Bulb planting depths vary depending on their size and species but as a rule of thumb, most bulbs can be planted at a depth of approximately 3 times their own height. Some tubers, such as Begonias, are best started off indoors or in a frost free greenhouse before transplanting outdoors. Full growing instructions can be found on individual product pages.

Bulb/Tuber When to plant bulbs Bulb Planting depths Planting distance between bulbs Position
Allium bulbs Autumn 10cm (4") 10cm (4") Full sun
Begonia tubers Spring 1cm (1/2") 30cm (12") Full sun, semi shade, dappled shade
Crocus bulbs Autumn 10cm (4") 7cm (3") Full sun, semi shade
Daffodil bulbs Autumn 10cm (4") 10cm (4") Full sun, semi shade
Dahlia tubers Spring 15cm (6") 45cm (18") Full sun
Bluebell bulbs Spring/Autumn 10cm (4") 10cm (4") Dappled shade
Gladiolus corms Spring 10cm (4") 15cm (6") Full sun
Hyacinth bulbs Autumn 10cm (4") 8cm (3") Full sun, semi shade
Iris reticulata bulbs Autumn 10cm (4") 8cm (3") Full sun
Lily bulbs Autumn 20cm (8") 15cm (6") Full sun, semi shade
Narcissus bulbs Autumn 10cm (4") 10cm (4") Full sun, semi shade
Ponerorchis tubers Spring 2.5cm (1") 7cm (3") Dappled shade
Ranunculus corms Autumn 8cm (3") 25cm (10") Full sun
Snowdrop bulbs Spring/Autumn 10cm (4") 10cm (4") Dappled shade
Tree lily bulbs Autumn 20cm (8") 15cm (6") Full sun, semi shade
Tulip bulbs Autumn 15cm (6") 13cm (5") Full sun
White Egret Orchid tubers Spring 2.5cm (1") 7cm (3") Dappled shade
Winter Aconite bulbs Autumn 5cm (2") 5cm (2") Full sun, semi shade, dappled shade

Quick guide:

How do you plant bulbs?

Plant bulbs with the pointed growing tip facing up. If it isn't clear, plant bulbs on their sides.

How do you plant bulbs in containers?

Bulbs are perfect for patio containers. Use good quality general purpose compost and mix in a handful of fine grit to improve drainage. You can also use specially prepared bulb compost. Water regularly through the growing season.

How do you plant bulbs in grass?

For a natural look, gently scatter bulbs and plant where they land. Use a trowel to dig a hole to the correct depth and drop the bulb in with the pointed tip facing up. Cover with soil and gently firm down to fill any pockets of air.

Visit our begonias hub page for more information on growing and caring for your begonias

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Written by: Sue Sanderson


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